The plant at Heysham, together with those at Stanlow and Billingham produced iso-octane additives required to raise 87 octane fuel to 100 octane rating. Initially, the limited size of the 100 octane fuel stockpile required strict rationing until supplies could be increased to meet requirements and the 100 octane fuel was dyed green to distinguish it from the 87 octane fuel which was blue.
Bulk supply contracts for higher octane fuel were placed by the Air Ministry and it was put into widespread use in the RAF in March 1940 when Spitfires' Rolls Royce Merlin engines were converted to use the 100 octane fuel.
By May 1940, reconnaissance Spitfires had begun flying combat missions using the 100 octane fuel. By 31 July 1940, there were 384 Spitfires serving in 19 squadrons using the 100 octane fuel.
A German aerial reconnaissance photograph, dated October 1940 and marked 'only for internal use', showed the oil refinery with some areas of the plant such as the boiler house, storage tanks (including those under construction), and flat-roofed warehouses being labelled on the photograph.
In 1941 the refinery was bombed: